Fetal brain-maternal aorta temperature differences in sheep

Abrams, Robert M.; Caton, Donald; Lb, Curet; Crenshaw, Carlyle; Mann, Lovepreet K.; Barron, D H

doi:10.1152/ajplegacy.1969.217.6.1619

Cited by 36 publications

(9 citation statements)

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“…Considering that pregnancy is a hypermetabolic and hyperdynamic state, perhaps a hypothermic response to infectious stimuli aimed at energy conservation, which defends the host's vital systems is of greater survival value than the antimicrobial and immunostimulating effects of a febrile response. Fetal Tc is normally "clamped" 0.4°C to 0.8°C higher than maternal Tc, (1), and in some species, such as the sheep, where the febrile response to bacterial pyrogen occurs until very late in gestation, fetal Tc increases in parallel (1,23) or exceeds (30) the rise in maternal Tc with a resulting increase in oxygen demand secondary to the temperature coefficient of metabolism (i.e., Q 10 ). If this occurred at a time when fetal oxygen availability was limited, such as asphyxia during birth, it could potentially exacerbate neuronal injury (11,31) and increase perinatal morbidity and mortality.…”

Section: Perspectives and Significancementioning

confidence: 99%

Metyrapone restores the febrile response to Escherichia coli LPS in pregnant rats

Alexander

Fewell

2011

American Journal of Physiology-Regulatory, Integrative and Comp

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Alexander BN, Fewell JE. Metyrapone restores the febrile response to Escherichia coli LPS in pregnant rats. Am J Physiol Regul Integr Comp Physiol 300: R1588 -R1595, 2011. First published April 13, 2011 doi:10.1152 doi:10. /ajpregu.00785.2010 an important component of the host's defense response to immune challenge, is absent or attenuated in rats near the term of pregnancy. The present experiments were carried out to determine the role of endogenous glucocorticoids in mediating the altered core temperature (Tc) response to exogenous pyrogen (i.e., Escherichia coli LPS). For the experiments, metyrapone-a glucocorticoid synthesis inhibitor-was administered to near-term pregnant rats prior to an EC100 dose of E. coli LPS. Administration of LPS following vehicle elicited a significant corticosterone response and resulted in a decrease in Tc (i.e., hypothermia). Prior administration of metyrapone, however, which abolished the corticosterone response and altered the pyrogenic/ cryogenic cytokine response to LPS, eliminated hypothermia and restored the febrile response. Our results provide evidence that endogenous glucocorticoids play a role in mediating the altered febrile response to immune stimuli observed in rats near the term of pregnancy.glucocorticoids; hypothermia; infection NUMEROUS PHYSIOLOGICAL CHANGES accompany the maternal adaptation to pregnancy in rats, including reversible changes in blood hormone concentrations (e.g., corticosterone) and basal thermoregulatory control, as well as the cytokine, prostanoid, and Tc responses to immune challenge (4,17,19,21,34). For example, Fofie and Fewell (21) observed that Tc responses to intraperitoneal administration of 160 g/kg Escherichia coli LPS (EC 100 in nonpregnant rats) are different in pregnant rats as early as day 10 of the 21-day gestational period compared with nonpregnant oophorectomized rats. In nonpregnant rats, 160 g/kg E. coli LPS elicits an increase in Tc (i.e., a fever) with a latency, magnitude, and duration of 1.5 h, 1.9°C, and at least 4.5 h, respectively (21). Accompanying the febrile response are significant increases in plasma IL-1␤, IL-6, TNF-␣, and IL-1ra (22). In pregnant rats, however, 160 g/kg E. coli LPS elicits a "regulated" decrease in Tc (i.e., hypothermia)-the magnitude and duration of which increase with increasing LPS dose and gestation-before a modest increase in Tc above baseline is recorded (21, 52); accompanying the hypothermia are significant increases in plasma TNF-␣, and IL-ra, but not IL-1␤ and IL-6 (22). The mechanism and consequences for the mother and fetus of this altered thermoregulatory component of the acute phase response remain largely unknown.It has long been known that glucocorticoids have an antipyretic action on natural fevers in man (27), and Coelho et al.(13) and Morrow et al. (38) have shown that endogenous glucocorticoids modulate bacterial pyrogen-induced fever in male rats. Furthermore, Moore and Fewell (36) have recently shown that oral administration of mifepristone (RU38486)-a progesterone and gl...

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Section: Perspectives and Significancementioning

confidence: 99%

Metyrapone restores the febrile response to Escherichia coli LPS in pregnant rats

Alexander

Fewell

2011

American Journal of Physiology-Regulatory, Integrative and Comp

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“…IMAI-MATSUMARA AND OTHERS In previous studies, fetal body temperature has been shown to parallel maternal temperature (Abrams, Caton, Curet, Crenshaw, Mann & Barron, 1969;Gunn & Gluckman, 1983). Therefore, when the body temperatures of pre-0-day pregnant rats in the present study dropped by 4 0C in the cold, fetal temperature probably decreased correspondingly.…”

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confidence: 96%

Suppression of cold‐induced thermogenesis in full‐term pregnant rats.

Imai-Matsumara

Matsumura

Morimoto

et al. 1990

The Journal of Physiology

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SUMMARY1. Thermoregulation against cold exposure was studied in rats during pregnancy and early lactation, and compared with that of virgin rats.2. When exposed to 0 TC for 60 min, rats which were within 24-48 h of parturition (pre-1-day rats) and those within 24 h of parturition (pre-0-day rats) showed significantly larger falls of colonic temperature (To) than virgin rats. The temperature decrease was greatest in the pre-0-day rats, being 4' 1 + 0 4 0C (mean + S.E.M.) at the end of cold exposure, compared with a decrease of 1-7 + 0-3 0C in the virgin rats. The tail skin temperature fell to 0 0C during cooling in all virgin rats and in pregnant rats at each gestational stage.3. During cold exposure at 10 0C for 30 min, pre-0-day rats also showed significantly larger falls in Tco (1I8+006 'C) than virgin (0-4+0-2 'C), pre-1-week (0-8 + 0 3 0C), post-0-day (0 3 + 0 3 0C) or post-I -week rats (0 4 + 0 3 0C). Although body weights in pre-0-day rats were far larger than those in virgin rats, the increase in oxygen consumption per animal during cold exposure was 50 % lower in pre-0-day rats (2-2 + 0 5 ml/min) than in virgin rats (5 3 + 0-3 ml/min). There was no difference in basal oxygen consumption per animal between the late pregnant and virgin rats.4. Within 24 h after parturition, both the decrease of Tco and the increase of oxygen consumption during cold exposure returned to the values observed in virgin rats.5. The present results demonstrate clearly that cold-induced thermogenesis is significantly suppressed in rats at a late stage of pregnancy.

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“…Since this kind of change is well correlated to a reduction in thyroid hormone secretion rate in the adult, the results suggest that the thyroid gland participates in active neuroen docrine regulation of heat production in the fetus. Previous studies have shown that the fetus is warmer than the mother by 0.5-1.0 °C and that the fetal-maternal tempera ture gradient is maintained during maternal hyperthermia induced by external heating [17][18][19][20]. It is therefore likely that fetal tem peratures in the vicinity of 41 °C were present in the heat-stressed ewes.…”

Section: Discussionmentioning

confidence: 99%

“…The difference in rectal tempera ture between the two groups was significant (unpaired t = 7.69, df = 18; p < 0.01). Since the normal fetomaternal temperature differ ence is maintained over a range of maternal temperatures [17][18][19], fetal temperature would probably be 0.6-1.0 °C above both the normal and hyperthermic maternal val ues and would therefore have reached 41 °C in the heated group [19], Fetal temperatures were not measured at autopsy, since the measurements would not accurately reflect fetal temperatures in utero.…”

Section: Emperaturesmentioning

confidence: 99%

Effect of Hyperthermia on Thyroid Structure in the Late Gestation Fetal Lamb

Andrianakis

Stephenson²,

Walker³

1990

Neonatology

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This study examined the effect of hyperthermia in late gestation on fetal thyroid structure. Mild heat stress (increase of ewe’s rectal temperature to 40.4°C) caused significant changes of fetal thyroid structure. Intra-follicular colloid area was significantly larger in the heat-stressed group (2,532 ± 181 μm²) compared to a control group where rectal temperature of the ewe was within the normal range (1,660 ± 188 μm²; p < 0.01). Epithelial cell height was significantly reduced (2.5 ± 0.19 vs. 4.8 ± 0.26 μm; p < 0.01). Fetal plasma glucose concentrations were significantly lower in the heat-stressed group (0.7 ± 0.07 mmol/l) compared to the non-heated group (1.0 ± 0.11 mmol/l; p < 0.05). We suggest that the fetal thyroid gland in sheep is responsive to environmental temperature changes and is important in the neuroendocrine regulation of fetal body temperature. Fetal hypoglycaemia may also contribute to the changes in fetal thyroid gland by altering the peripheral utilization of thyroid hormone. Such changes, if prolonged, may contribute to the decreased rate of fetal growth and maturation associated with chronic heat stress in sheep.

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Fetal brain-maternal aorta temperature differences in sheep

Cited by 36 publications

References 0 publications

Metyrapone restores the febrile response to Escherichia coli LPS in pregnant rats

Metyrapone restores the febrile response to Escherichia coli LPS in pregnant rats

Suppression of cold‐induced thermogenesis in full‐term pregnant rats.

Effect of Hyperthermia on Thyroid Structure in the Late Gestation Fetal Lamb

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